1. Field of the Invention
This invention relates to an extension splint that lengthens the muscle and soft tissue about an extremity or limb synovial hinge joint to assist in rehabilitating flexion contractures caused by soft tissue injury. More particularly, the invention relates to a three point extension splint to treat flexion contractures about the knee, elbow and/or finger.
2. Description of the Prior Art
Joint contractures are a common complication following fractures, dislocations, and soft tissue injuries about the synovial joints such as the elbow and knee. Perry noted in Prescription Principles, American Academy of Orthopaedic Surgeons: Atlas of Orthotics; Biomechanical Principles & Applications, pp 120-122, St. Louis, C. V. Mosby, 1975 that, "restoration of full elbow extension is a strong challenge," and that, "recovery of lost arcs of motion with an orthosis is difficult."
Kottke et al. in The Rationale for Prolonged Stretching for Correction of Shortening of Connective Tissue; Arch. Phys. Med. Rehabil., 47, pp. 345-352, 1966 suggested that prolonged stretching at moderate tension resulted in a significantly increased range of motion about a joint over that achieved by intense short duration stretching. In summary, Kottke stated that,
mobility of loose or areolar connective tissue is related to its structural organization as a meshwork of fibers. The range of mobility depends on the distance between the points of attachment of the collagen fibers. In dense connective tissue, that has little mobility, the fiber meshwork has smaller interstices than those in loose connective tissue with considerable freedom of motion. Normal connective tissue develops a tensile force, that causes a slow, progressive shortening of that connective tissue until stopped by an opposing force. This property of progressive shortening is responsible for the contractures, that develop in soft tissues around joints when motion is limited or prevented. The attachments between collagen fibers show high resistance to suddenly applied tension but relax or creep when exposed to prolonged tension. Utilizing this plastic characteristic of connective tissue, methods have been developed for hip flexors, knee flexors, and ankle plantar flexors. Significantly greater restoration of the motion of these has been obtained, within the limits of pain and without evidence of tearing of tissues, by prolonged stretching at moderate tension than by intense stretching of short duration.
The original treatment to create the prolonged stretching at moderate intensity was to apply a succession of casts where each cast was fixed in a greater angle until the joint was straight. At best, this was inconvenient to body maintenance such as washing. At worst, it took months of incapacitation and lead to a deterioration of other muscle groups.
Others have designed devices to replace the cast method. These devices are all based on some variation of a three point extension. Best, in U.S. Pat. No. 4,612,919 issued Sep. 23, 1986, describes an adjustable limb support designed to provide this slow stretching with some control in the hands of the patient. The Best device has a rigid metal frame work that appears to be heavy, cumbersome and does not appear to contemplate or provide for the use of variable pressure intensities during the course of the day. Also, Best does not provide easy adjustment to the patient or a device that is secure and safe to both patient and sleeping companion if the device is worn while sleeping.
Brown, in U.S. Pat. No. 4,665,905 issued May 19, 1987, describes a lighter weight, wire frame dynamic elbow and knee extension brace. The Brown brace appears to have an adjustable length, but not an adjustment for the tension created by the spring arrangement.
Green et al., describes a turnbuckle orthotic correction device in J. Bone and Joint Surgery, Vol 61-A, No. 7, pp 1092-1095, October 1979. B. C. Parker describes another variation of a dynamic elbow extension splint in American J. Occupational Therapy, Vol. 41, No. 12, pp 825-826, December 1987. Yet another variation of a gear controlled dynamic extension splint is taught by Mitchell in U.S. Pat. No. 5,036,837 issued Aug. 6, 1991. A dynamic traction device for the finger is illustrated by Schenck in U.S. Pat. No. 4,724,827 issued Feb. 16, 1988. These devices do not provide a light weight easily adjustable dynamic extension splint that can provide myofascial release.